Regretfully, there are many factors outside the theme's control that could slow a site down. Try following our Performance Guide. Regretfully, we could not help with website optimization other than showing you a general guide as I have said, there are many factors outside of the theme's control that could slow a website. If your site is still slow after following the guide, you will need to consult with a new website speed contractor.
If you're referring to using Cornerstone, there is currently an element limit where if you are near to using 200 elements in a page, it could slow the performance. The solution would be to design your content wisely like using a grid plugin to display a gallery rather than setting up lots of columns and image elements.
Thank you for understanding.